Heat insulation



| B. MILLER ETA| HEAT INSULATION Filed June 29, 1942 a v3 IIardKPatented Aug. 31, 1948 um'rso STATES PATENT, orrics m'r INSULATION LewisB. Miller, Ambler, and-Willard R. Seipt,

alsimrl North Wales, Pm,

Mattison Company, Ambler, Pa

of Pennsylvania to Kealbey & a corporation Application June 29, 19,Serial No. 448,928

Claims. 1

This invention relates to heat insulation, and particularly toinsulation adapted for use over a wide range of heat conditions and upto relatively high temperatures.

The object of the invention is to provide an insulation which will havelow density for the relatively high temperature which it is adapted towithstand.

A further object is to provide an inexpensive, adaptable process for theproduction 01' such insulation composed of a combination of fibrous andpowdery materials.

In the accompanying drawing Figs. 1, 2 and 3 are diagrammatic viewsillustraging one method of producing the insulation, an

Fig. 4 is a perspective view of the insulation in rectangular blockform.

The raw materials are composed of fibers, a powdered filling materialand a powdered binder. Preferably the fibrous material is asbestos inthe form of amosite, this being in proportion of 25- 40%. The powderedfiller is diatomaceous earth in proportion of 35-45% and the powderedbinder is bentonite in proportion of 25-30%, all of the proportionsbeing by relative dry weights.

In the formation of the insulation the raw materials are firstproportioned and dry mixed so that the powdery materials are wellblended and distributed among the asbestos fibers giving a very open,fiufiy structure. This ilufiy material is then spread in a thin layer Ion a base or on a movable support, such as an endless belt or rotarytable in case of a continuous process. In Fig. 1 of the drawings thebase 5 has a layer 1 of the material within a surrounding rim orretainer 6.

means of an atomized spray, the mixture of materials in dampened formthus being built upto desired depth on the base plate, belt or table.

The accumulated dampened mass of asbestos,-

instance, as indicated in Fig. 3 with the block insulation, plunger 2!may be used within the rim or retainer 8 to press the layers into morecompact dorm, designated 8, this compacting being variable in amountdepending upon the desired density of the final insulation. The resultis a rectangular insulating block 8 as illustrated in Fig. 4 with theupper and lower surfaces in and the edge surfaces 9. In this block thetendency is for the fibers, particularly the long ones, to run ilatwisewiththe layers; however, in each layer the fibers may run in alldirections and may even run from one layer to another, and entangle withthe powdery materials, all of the surfaces of the mixture being evenlydampened.

The shaped piece is then dried driving off the moisture and developingthe adhesive bond of the bentonite between the particles of diatomaoeousearth and between the asbestos fibers and the other materials, theparticles of the whole mass being thoroughly cemented together to im- Drt great strength to the block as a whole.

During this drying the bentonite is subjected to a heated moisture-ladenatmosphere as the wetting water is vaporized and the bentonite is Thethin layer I of raw materials is then uni- Preferably an air spraynozzle 20 is used to eflect the moistening, the water being atomized byan air jet so as to form a cloud or mist penetrating and permeating thelayer 1 from surface to surface.

Successive layers 1 are then accumulated on top of each other one by oneas indicated in Fig. 2, each layer of the fibrous powdery mixture beingdampened down as above described by supplied with moisture from themixture of fibers and diatomaceous earth, the great surface areas ofwhich adsorb the atomized moisture. If desired. this moisture treatmentmay be accentuated by steaming the shaped pieces for a few minutesbefore drying further to develop the binding effect. After drying theshaped and dried pieces are ready for packaging.

By this method insulation which will withstand 1000 to 1200 F. may bemade with a density of six to eight pounds per cubic foot and insul a.tion withstanding a temperature of 900?;to 1000 F. may be made with adensity as low as 3.9

pounds per cubic foot and with sufilcient strength for usual serviceconditions. A light weight high temperature thermal insulation willresult when the mixture is compressed under a pressure of about fiftypounds per square inch or less to give a final product weighing elevenpounds per cubic foot and capable of withstanding a temperature of atleast 1900 F. and in the neighborhood of at 1900 F. is 1.05%

l a 2200 F. to 2300" F. for the higher pressures and densities.

The density of the final product will depend upon the degree to whichthe dampened mixture is compressed and this centre very accuratelypredetermined depending upon the insulating surface to which the productis to be put". A

is 30.0, the Pusey and Jones hardness 1.10 and under the Navy abrasiontest the percent loss in ten minutes is 43 and in twenty minutes 6'7. At850 F. the modulus of rupture is 17.6 and'the linear shrinkage 0.35%; at1100 F. the modulus of rupture is 14.3 and the linear shrinkage is0.59%: at 1500 F. the modulus of rupture is 13.? and the linearshrinkage 1.10%; and at assures 4 a I. v V v terial may be appliedwithout failure is considerably dependent on the composition of theproduct. The light weight product composed of bentonite and fiber in. thratio of about -70 has a density variable ordinarily from about fourpounds per cubic foot to eight pounds per cubic foot and will tdndtodisintegrate beyond usefulness above a temperature of about 900 Withless fiber ftype of "composition using still less fiber and morediatomaceous earth (30 parts fiber, parts diatomace'ous earth and 30parts bentonite) will shrink somewhat above 1900 F. and will be used1900 F. the modulus of rupture is 19.8 and the linear shrinkage is1.77%, these latter figures being on the basis of a six hour soakingheat} subjecting the whole piece to the temperature indicated. Undernormal conditions of usage insulations are subjected to hightemperatures only upon one side and any thermal deteriorationencountered is therefore in general less in practice than under theconditions of the test.

In conductivity th present'insulation is very low being only about ofthe standard high temperature insulations up to 700 F., and is distinctly superior in the lower ranges of temperature, i. e., below 1000F. The higher densities and larger proportions of diatomaceous earthrender the insulation more eifective at higher temperatures and thecomposition oi a corresponding block or other shape may be varied to bedenser at the portions adjacent the heated surface. Larger proportionsof the diatomaceous earth may also be used at these portions of theinsulation by correspondingly varying the composition of the successivelayers i and variations in density may be effected by subjecting theearlier deposited layers to separate higher compacting pressure so thata plurality of pressures successively lower in intensity are used toproduce the block or other shape.

The material in dampened form is relatively plastic and may be pressedto any desired shape and will retain. this shape during drying. Nopressures are required in the drying operation and the material isself-setting in that the drying operation does not require the shape tobe retained in the shaping mold.

The drying shrinkage of the blocks is negligible and'they may be castsubstantially to the exact size of the finished piece.

This insulation is relatively simple in manufacture and low in cost andwidely adaptable'to different conditions of use.

The heat insulation of this invention combines mineral fibers, such asasbestos or rock wool with powdery particles, to give a highly porousunit structure withstanding a very high temperature in proportion to thedensity of the insulating material. It maintains its form undercontinuous six hours heating at least to the temperatures as abovedescribed. The withstood temperature or the maximum temperature to whichthe mo,-

at densities of eleven pounds per cubic foot to sixteen pounds per cubicfoot. Thus the maximum temperature is relatively high in relation to thedensity of the insulation.

In place of the bentonite or in conjunction with it, other binders maybe used, such as kaolins or other clays in temperatures up to 1900 F.silicates may be used in place of the bentonite, but only up totemperatures of about 700 F. while gums and other emulsified or watersoluble organic binders may be employed up to about 200-300" F. To givetemporary strength at normal air temperatures and facilitate handlingbefore and during application of the insulation, a small. percentage ofa water soluble gum may be added as an additional binder. Other fibermay also be used in place or together with the amoslte such aschrysotile and. 'amphibole asbestos up to 2:900 R, rock wool or glasswool up to 1000 F. or organic fibers up to 200 F.

' In the formation of these insulations the characteristics arecontrollable by the proportions of the ingredients and by the compactingpressures employed making the insulation widely adaptable while at thesame time maintaining a relatively low density in proportion to thetemperatures involved. This represents not only a saving in weightand-material over prior insulations but is accompanied by a. lowerconductivity as above explained. 4 v

' The process for producing the product of this invention is describedand claimed in our cobendingapplication Serial No. 534,650, filed May8,- 1944.

We claim:

1. A heat insulating structure formed by a series of layers of similarcomposition, each layer comprising whole mineral fibers in proportion ofthe order of 25 to 40% by dry weight and tending to run fiatwise of thestructure and entangled with evenly distributed separate particles ofpowdery mineral material and evenly distributed separate powderyparticles of a binder material of the group bentonite, clays andsilicates of the order of 25 to 30% of the dry weight of the insulationand set in place adhering to the fibers and to the powdery'material andto each other by surface contact between the individual fibers andindividual particles leaving intervening voids to provide an open highlyporous structure having a low density of the order of 8 to 15 lbs. percu. ft. and capable of withstanding for at least six hours a temperaturein degrees F. which is over times the weight of a cu.-ft. of theinsulation.

2. A heat insulating structure as set forth in claim 1 in whichsuccessive layers of the structure vary in density and correspondinglyvary in heat resistance. j

"' A heat insulatingstructure' as set forth in 5 claim 1 in whichsuccessive-layers vary in the proportion of powdery material andcorrespondingly vary in heat resistance.

4. A heat insulating structure comprising whole mineral fibers inproportion of the order of 70% by dry weight and tending to run ilatwiseof the perature in degrees 1". which is over 200 times the 5 weight 01'a cu. ft. of the insulation.

5. A heat insulating structure composed of 25-30% of a bonding materialof the group bentonite, clays and silicates and the remaindernoncementitious mineral particles including whole mineral fibers formingat least 25% 01' the entire composition, the bonding material being inthe form of powdery particles intermixed and. entangled and evenlydistributed among the noncementitious particles and bonded thereto bysur-.

face contact between the individual particles of the bonding materialand the individual non-- cementitious particles to provide an openhighly porous structure having a low density of the order of 4-15 poundsper cubic foot and capable oi withstanding for at least six hours atemperature in degrees F. which is over 100 times the weight of a cubicfoot of the insulation.

6. A heat insulating structure as set forth in claim 5 in which thenoncementitious mineral 5 material is composed of asbestos anddiatomaceous earth.- 7 1 4 LEWIS a. mum. I wmaan a. sm 'r.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 248,324 Johns -1 Oct. 18, 18811,045,933 Belknap Dec. 3, 1912 1,387,348 Burgstresse'r Aug. 9, 19211,513,723 Bohlander Oct. 28; 1924 1,544,196 Teitsworth June 30, 19251,568,415 .Pilllod Jan. 5, 1926 1,613,137 Seigle Jan. 4, 1927 1,715,977Bates et a1. June 4, 1929 1,830,253 Bechtner Nov. 3, 1931 1,851,038Clark Mar. 29, 1932 1,887,726 Weber Nov. 15,1932 2,008,718 Jenkins -..s-July 23, 1935 2,033,106 Cummins Mar, 3, 1936 2,184,316 Plummet -Dec. 26,1939 2,276,869 Pond Mar. 17, 1942 I 2,309,206 Newman Jan. 26. 1943MacArthur et al. May 16, 1944

